This invention relates generally to diesel engines and, more particularly, to a method and system for altering actual fuel injection timing relative to conventional fuel injection timing set by an engine manufacturer without having to change an engine""s sensors, electronic controller or fuel injectors.
Diesel engine manufacturers and users, particularly railroads, face serious challenges in further reducing emissions. Emissions from diesel engines have been under increasing scrutiny in recent years and standards are becoming stricter. The 1990 Clean Air Act Amendments mandated the U.S. Environmental Protection Agency (EPA) to establish emission standards for locomotives. Diesel engine exhaust is a heterogeneous mixture which typically includes gaseous emissions such as carbon monoxide (CO), unburned hydrocarbons (HC) and oxides of nitrogen (NOx), as well as condensed phase materials (liquids and solids) which comprise so-called particulate matter (PM). While the EPA""s goal is to reduce all emissions, a primary focus in recent years has been to reduce NOx, a major component of smog and acid rain.
In general, current EPA regulations set forth at 40 C.F.R. xc2xa792.8 provide a three-tier system for limiting emissions of NOx, PM, CO and total hydrocarbons (THC) as well as other compounds from locomotives. The regulations provide separate standards for line haul locomotives (i.e., locomotives used to power freight train operations over long distances) and switch locomotives (i.e., locomotives that are designed or used solely for the primary purpose of propelling railroad cars a short distance and are powered by an engine with a maximum horsepower rating of 2300 hp or less). Tier 0 standards generally apply to locomotives and engines used in locomotives manufactured on, or after, Jan. 1, 1973, and before Jan. 1, 2002; and upgraded locomotives manufactured prior to Jan. 1, 1973. Locomotives and engines used in locomotives manufactured on, or after, Jan. 1, 2002, and before Jan. 1, 2005 are subject to Tier 1 standards. Locomotives and engines used in locomotives manufactured on, or after, Jan. 1, 2005 will be subject to Tier 2 standards. Table 1, below, provides a summary of certain emission limits in grams per brake horsepower hour (g/bhp-hr).
Emission reduction methods to-date have materially compromised fuel efficiency, an undesirable side effect from both an ecological and economic standpoint. Railroads cannot afford to substantially compromise fuel efficiency. Since fuel costs make up a significant portion of the operating costs for a railroad, any substantial compromise in fuel efficiency can substantially increase overall costs. Increased fuel consumption raises costs to the railroads and their customers. Greater demand for fuel increases costs, which affects the economy and the environment as suppliers seek to meet the demand. The environment is affected directly by the increased demand for fuel and indirectly by the inevitable shift of some freight to trucks, which emit an estimated three times more pollutants per ton moved than trains.
Injection timing, which is the time during a cycle at which diesel fuel begins to enter the combustion chamber, affects both fuel economy and emissions, particularly NOx emissions. For example, retarding injection (i.e., starting injection later in the cycle) often has the effect of reducing NOx emissions at the expense of fuel economy. The retarded fuel injection timing lowers the firing pressure in the cylinders resulting in a low cycle efficiency and leading to increased fuel consumption.
Using a one-size-fits-all approach, modern diesel engines employ electronic controllers having injection timing algorithms and tables of predetermined fuel injection timing values to govern injection timing. Each manufacturer typically selects timing values to meet then-prevailing regulatory requirements and achieve the manufacturer""s own performance, operating efficiency and emissions objectives. The electronic controller produces, among other signals, an injection timing signal (i.e., a signal that determines the start of fuel injection in a cylinder) based on the preset timing values and the current operating state of the engine as indicated by output from one or more sensors. Thus, at a certain RPM, an electronic controller may generate certain pre-determined injection timing signals.
A problem with a one-size-fits-all approach is that the timing values selected by a manufacturer may not meet the performance, operating efficiency and emissions objectives of users. For example, a railroad may wish to achieve a certain acceptable range of NOx emissions at a maximum attainable fuel economy within that range. While these objectives may be achieved by altering injection timing relative to factory-set injection timing, conventional diesel engines do not provide cost-effective means for accomplishing this. Additionally, manufacturers may be unwilling to produce an electronic controller tailored for the preferences of one customer, or to allow third parties to adapt the manufacturer""s proprietary coding and algorithms implemented by the electronic controller.
Accordingly, it would be desirable to provide a cost-effective system and method for altering fuel injection timing in a conventional diesel engine to achieve a determined range of acceptable emissions at an acceptable level of fuel consumption that may be used with OEM sensors, electronic controllers and fuel injectors.
It is therefore an object of the present invention to provide a cost-effective system and method for altering fuel injection timing in a conventional diesel engine to achieve a determined range of acceptable emissions at an acceptable level of fuel consumption within that range.
It is another object of the invention to provide an interceptor module for intercepting signals intended for an electronic controller to produce injection timing signals and altering the intercepted signals to cause the electronic controller to produce injection timing signals that result in a determined range of acceptable emissions at an acceptable level of fuel consumption within that range.
It is also another object of the invention to provide a means for altering fuel injection timing in a conventional diesel engine to achieve a determined range of acceptable emissions at an acceptable level of fuel consumption within that range for use in connection with an OEM electronic controller and OEM fuel injectors.
It is yet another object of the invention to provide a means for altering fuel injection timing in a conventional diesel engine to achieve a determined range of acceptable emissions at an acceptable level of fuel consumption within that range without causing an electronic controller to generate a fault or error code.
To achieve these objects, a system for altering injection timing is provided according to one aspect of the subject invention. The system includes an interceptor means for intercepting signals intended for the electronic controller to produce injection timing signals. The interceptor means alters the signals, such as by introducing a time shift (either advancing or retarding the signal), and transmits the altered signals to the electronic controller. The altered signals cause the electronic controller to produce an injection timing signal desired by the user.
A module for intercepting injection timing signals from one or more sensors and introducing a determined time shift is also provided according to another aspect of the present invention. The module includes a micro-controller module for introducing a time shift to the intercepted signals and an interface module for filtering the time shifted output from the micro-controller module and interfacing with the electronic controller, causing the controller to produce desired injection timing signals.
A methodology for altering injection timing is also provided according to yet another aspect of the invention. The method includes steps of determining desired injection timing signals relative to factory-set injection timing signals, intercepting signals intended for an electronic controller to produce injection timing signals based on the factory-set injection timing values, altering the intercepted signals, such as by introducing a time shift, to cause the electronic controller to produce desired injection timing signals relative to factory-set injection timing signals, and transmitting the altered signals to the electronic controller.